Tim Dunn and Siddy Holloway explore the abandoned branch line between Holborn and Aldwych. And at Holloway Road they find out about the Tube's only spiral escalator.

Visit one of London Underground’s most secret places: North End under Hampstead Heath. Abandoned before completion, the station became a Cold War bunker.

Explore the disused parts of Piccadilly Circus, the grandest station on the London Underground. And they also visit the long-abandoned Highgate surface station.

Have a night-time track walk exploring long forgotten stations on the District line in Whitechapel. And they discover how sprawling Oxford Circus was first built.

Explore Clapham South deep level shelter, where thousands of Londoners slept in the war. They also visit Moorgate, and the remains of a tunnelling machine there.